Recently, ultra-high-density storage devices employing three-dimensional (3D) memory stack structures have been proposed. Such memory stack structures can employ an architecture known as Bit Cost Scalable (BiCS) architecture. For example, a 3D NAND stacked memory device can be formed from an array of an alternating stack of insulating materials and spacer material layers that are formed as electrically conductive layers or replaced with electrically conductive layers. Memory openings are formed through the alternating stack, and are filled with memory stack structures, each of which includes a vertical stack of memory elements and a vertical semiconductor channel.